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Math Help - Elevation on Weight

  1. #1
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    Elevation on Weight

    If an object weighs m pounds at sea level, then its weight W (in pounds) at a height of h miles above sea level is given approximately by the function

    W(h) = m[(4000)/(4000 + h)]^2

    If Amy weighs 120 pounds at sea level, how much will she weigh on Pike's Peak, which is 14,110 feet above sea level?
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    Quote Originally Posted by magentarita View Post
    If an object weighs m pounds at sea level, then its weight W (in pounds) at a height of h miles above sea level is given approximately by the function

    W(h) = m[(4000)/(4000 + h)]^2

    If Amy weighs 120 pounds at sea level, how much will she weigh on Pike's Peak, which is 14,110 feet above sea level?
    For this question, you just have to substitute the value into the function after converting feet into miles.

     W(h) = m\left[\frac{4000}{4000 + h}\right]^2

    1\text{ foot} = 0.000189393939\text{ miles} \implies 14100\text{ feet}\approx 2.67045455\text{ miles}

    Substituting this value (along with the weight in pound) into the function and it will give you weight on Pike's Peak. Round of your final answer to an appropriate significant figure.
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  3. #3
    Member OnMyWayToBeAMathProffesor's Avatar
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    reply

    would the answer be 120\left[\frac{4000}{4000 + 2.67234848}\right]^2=119.9999464?
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    Can I???

    Can I round 2.67045455 to nearest unit and use it as the miles?

    How about to the nearest tenths and use it as the miles?
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    Quote Originally Posted by OnMyWayToBeAMathProffesor View Post
    would the answer be 120\left[\frac{4000}{4000 + 2.67234848}\right]^2=119.9999464?
    Yes, I get 120pounds when rounded to an integer value.

    Quote Originally Posted by magentarita View Post
    Can I round 2.67045455 to nearest unit and use it as the miles?

    How about to the nearest tenths and use it as the miles?
    Yes, you can. For accuracy, it's best to keep it to as many significant figures but you can round the unit. You decide on the appropriate degree of accuracy. If the question asks you to give the final answer to 2dp then you should use the round the digit (of the unit to be put into the function) to 3dp (or 4dp for further accuracy).

    EDIT: Personally, I would round to 3sf (2.67) and use this value as the the data provided for the question use integers hence the final answer should be given as an integer so for accuracy, 2dp unit of miles would be adequate.
    Last edited by Simplicity; July 21st 2008 at 03:44 AM. Reason: Typo
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  6. #6
    Member OnMyWayToBeAMathProffesor's Avatar
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    Yes, I get 120miles when rounded to an integer value.
    'Air', don't you mean 120 pounds not miles?
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    Quote Originally Posted by OnMyWayToBeAMathProffesor View Post
    'Air', don't you mean 120 pounds not miles?
    Sorry, my bad. Yes, that is what I meant. I had 'miles' in my mind as that was my next topic of discussion so wrote that as opposed to 'pounds'. It corrected now, Thanks!
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    I thank all of you

    It's great to have several replies to questions.
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